i have to add coolant on a weekly basis, i don't see a leak, heater core has already been replaced last year, no coolant apparent in oil, hoping it's not a head gasket, could it be anything else?

 

Yes! I had a coolant leak from time to time. I even replaced the radiator as it would pool a small amount of coolant at one corner of the car. It turned out that the overflow plastic tank had a crack under it at the seam and would leak from time to time under certain conditions. It would leak and run down some metal channel to make it look like it was coming from the radiator. Good luck!

 

Read this:
https://volvoforums.com/forum/volvo-...roblems-63516/

 

rspi, did you ever find out what the problem was?

 

Check the seal underneath the expansion tank for the rubber pipe that connects to the engine block, and then check where the pipe connects to the engine. Another place where is is possible you have a leak are the turbo coolant pipes. These are hard to see, and are probably best observed from under the car. If you can't do that, remove the heat shield on the left side of the engine, as you look at it, at the back of the block and above the turbo, so you can see the turbo and its oil and cooling pipes. A coolant leak should be quite evident, as it will have left a stain. You could test for where the leak is by filling the expansion tank to the fill/normal level and then putting a large sheet of cardboard under the engine, and running the car for a while. Look for signs of leaks on the cardboard, and you'll know the area of the problem. I'll bet you'll see leaks near the back of the engine, coming from the turbo pipes.

 

Uh oh. We had the same problem last year with our 2000 S70. I replaced everything under the sun. We finally had the head gasket replaced and that seemed to work for a while, a short while, maybe a few months. Had to take it in again and found the block was cracked. Very expensive venture. We replaced the engine and all seems well. We have other issues, but my wife loves her car and so we keep sinking money into it.

 

As the thread I had tells all of my woes in dealing with it. It was a bad head gasket. If the car hasn't overheated, you likely will not have a cracked block. If you have a cracked block, you will surely have a miss in one of the pistons and coolant mixing with the oil.